This invention relates to a method of extracting a mask pattern for an electron beam exposure, and in particular, to an electron beam cell projection lithography.
Recently, a design rule (that is, a minimum line width) of an ultra-large-scale integration (ULSI) has been reduced to a critical state. Therefore, as long as an optical lithography technique is used, it is difficult to fabricate the USLI by the use of such an optical lithography technique.
To solve this problem, an electron beam direct delineation technique has been proposed.
However, the electron beam direct delineation technique has a poor throughput as compared to the optical lithography technique, since in the electron beam direct delineation technique, the exposure is performed by successively scanning a focused electron beam to delineate a pattern.
In order to improve the throughput, an electron beam cell projection lithography technique has been developed.
In such an electron beam cell projection lithography, a mask is used to perform the electron beam exposure like the optical lithography.
In the electron beam cell projection lithography, a mask pattern is extracted from a design pattern data with a maximum beam size of the electron beam or a beam size similar to the maximum size.
As the mask pattern, a pattern which is repeated in the design pattern is generally selected. By using this mask pattern, the electron beam exposure is performed.
The conventional extracting method is disclosed in Japanese Unexamined Patent Publication No. H5-343304. In the conventional method, the repeated pattern is mechanically extracted with a partial beam region similar to the maximum beam size from a design pattern.
In the conventional method, a pattern having the same line width is divided. By using the extracted pattern, a mask for the electron beam exposure is formed. Further, by using the mask, the electron beam exposure is performed. This electron beam exposure is performed by successively moving a partial shot region.
However, in this case, the exposed patterns are connected to each other with the same line widths at the boundary of the shot region, resulting in a registration error. The registration errors cause deterioration of dimension accuracy of a printed resist pattern. Since in accordance with the recent high integration and high finalization, dimension accuracy of 0.02 .mu.m or less is required, it is indispensable that the registration error is eliminated.